My question is this: I have always had a problem blowing speakers by playing them too loudly. Can anybody tell me how loud I can play based on the hardware I am using. I am not technical at all when it comes to this stuff.

The most common cause of blown speakers is clipping. Your speakers may be rated at way more (2x,3x) power than your amp and you can still easily blow them.

If you set you volume to high when playing content with high dynamic range typically action movies, the spikes will easily exceed the limit of the output stage and cause it to clip. When the signal clips, you get DC current. DC is fatal to speakers. An amplifier of say 80 watts can easily fry a 400 watt M80 if it clips excessively.

Because you say you have blown many speakers, you are setting the volume too high. With the sound dynamics movies produce today, if your receiver is set to full dynamic mode (i.e. not night, evening etc...), you should really not be setting the volume more than about 1/3 (just a guess). Your Denon has Audyssey, try enabling dynamic volume and set it to evening mode, which should tame the spikes so you can do a general volume increase.

Or you can be a maniac like me and get an ADA1000 or other good amp to drive the fronts and even center. I have a Denon 4311CI and I use 3 channel ADA1000 my M80s and VP150.

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DD, quality speakers such as your M80s can't be blown simply by playing them too loudly. Your ears would give out well before the speakers would. What could possibly happen would be damage resulting from the amplifier clipping if it couldn't supply the power needed.

Looking at your hardware, it clearly is capable of sound levels beyond what's safe to your hearing. If you're speaking of a movie at -8dB, if your setup is correctly calibrated that equates to about 97dB(the max peak in a movie channel is 105dB). This peak would require about 20 watts for the M80, so louder would be possible, but most listeners, including me, consider that to be loud enough for home listening.